IMPROVED PLASMA JET SYSTEM

摘要

A plasma jet CVD system (100) includes gas injectors (122a-122h) and a stand-off ring (126). The gas injectors have outlet holes (236a-h) preferably flared to approach the expansion angle of the injected jet, thereby keeping the holes substantially free from entrained atomic hydrogen. The injectors are arranged counter-rotational to the swirl of the primary jet, providing a more uniform mixture of hydrocarbons and atomic hydrogen. The stand-off ring provides vents (152a-152d) for cooler gases to enter the nozzle (128), thereby decreasing the overall temperature of the injectors and decreasing the temperature gradient experienced by the injectors, thereby preventing injector cracking. In addition the vents reduce shear, thereby increasing jet velocity and increasing the deposition rate for the coating. In addition, a new method of injector design permits optimal mixing characteristics to be obtained across various recipes whereby the ratio of the mass flux of the primary flow of the jet to the mass flux of the injected flow from the downstream injectors is kept constant.